A very small value of inter-electrode capacitance is a main factor limiting image spatial resolution of electrical capacitance tomography. The front-end sensing circuit of multichannel capacitance tomography system EVT4 was designed for measurement of extremely small capacitance values in the range from 1 fF to several pF. The capacitance value is determined by charging it using a single high voltage pulse and integrating a charging current. The idea of gain adjustment in the front-end amplifier of a capacitance measurement circuit is presented. The switchable feedback loop of the inverting preamplifier-a first stage of the sensing circuit-enables gain adjustment in a wide range. The measurements using a cylindrical 2-D capacitance sensor were performed without and with gain adjustment. The obtained results showed improvement of signal-to-noise ratio for the pairs of opposite electrodes from about 22 to 30 dB.

A new method of capacitance measurement for electrical capacitance tomography is presented. A single-shot excitation is used to accelerate measurement. A high-voltage pulse and oversampling of received signal are applied to obtain an acceptable signal-to-noise ratio. The results of measurements of standard capacitors and mutual capacitance of electrodes in 16 electrode tomographic sensors are presented. The elaborated circuit is stray-immune. It can measure capacitance in a range from about 1 fF to 1 pF at one gain setting with good linearity and precision at the rate of 20 000 samples per second.

Three-dimensional (3D) visualization has provoked interest in electrical capacitance tomography (ECT) due to recent progress in the development of capacitance measurement circuits and data-acquisition systems. This paper proposes image reconstruction using spatio-temporal sampling in the Z-axis for 3D ECT to improve spatial image resolution. In a typical application of ECT, multi-phase flow imaging is performed through two-dimensional (2D) data acquisition and 2D reconstruction of image frames over time. In the presented method, a volume of interest (VOI) is reconstructed from several time samples obtained using a 3D sensor. The procedure of Jacobian matrix extension for the spatio-temporal data is described. The experiments were carried out using the EVT4 system and a 32-electrode sensor. The reconstruction results of a VOI from a single 3D measurement and spatio-temporal sampling are compared. A phantom for 3D imaging to assess spatial image resolution using a modulation transfer function is proposed.

A desirable feature of hospital information systems is interoperability, which is generally quite limited due to the lack of standardization of the data model. This results in high development and maintenance costs for such systems. The openEHR standard addresses this problem. Due to its two-level modelling, it allows the separation of demographic and medical data and the storage of this data so that it can be easily processed and exchanged. However, it introduces an additional software layer that may affect system performance. This article examines the performance of a system based on the openEHR standard and compares it with the performance of a proprietary system developed in a classic way. Two hospital information systems with the same functionality were designed and developed. One was based on an openEHR server, and another was using proprietary data model having both demographic and medical data. Systems were deployed on Azure platform and load tests using JMeter were conducted to calculate statistics of elapsed time of requests as well as throughput of both systems. Endpoints which fetch only demographic data had the same performance, but when medical data had to be queried, a decrease in performance of the openEHR based system was noticed. The system based on a proprietary data had about 6 times bigger throughput in terms of medical data fetching. OpenEHR adds another layer to the architecture of a hospital information system which might result in performance issues. Such a system must be designed to operate on a sufficiently strong architecture if it is intended to serve many users.